[avidiax]

The one that's the most neglected is natural lighting. Light pipes, solar collectors, and microprism window treatments are all available.

The second thing is white paint. You need less outdoor lighting if the built environment absorbs less light.

[tremon]

You're going to need very long light pipes to use natural lighting for your digital signage at night. Are you really sure that's a better option?

[wikfwikf]

This does not solve the problem of filling city centers with huge company logos, adverts, signs for casinos or night clubs.